Bent Hasholt

Present-Day Climate at Zackenberg

Publisher Summary This chapter outlines the most prominent parameters of climate at Zackenberg and focuses on the short-term spatiotemporal variations of these parameters within the valley Zackenbergdalen and along the east coast of Greenland. The individual climatological parameters demonstrate large spatiotemporal variations. The greatest variations occur in winter when the differentiated influence of the solar energy is low or equal to zero, but this is connected to the fact that in the cold winter period, the cyclonic activity is more intensive and frequent than in the warmer summer period. In addition, the temperature contrast between the arctic air and the advected air from the mid-latitudes is highest during this period. In turn, the effect of the underlying surface is not large because snow and sea ice cover almost the entire arctic area. In the warm summer period, the solar radiation is the most important climatological element, and it causes the greatest heterogeneity of the meteorological elements in all spatial scales: micro-, macro-, and topo-climatic. The albedo of the underlying surface that is significantly differentiated increases the influence of solar radiation in the radiation balance. However, because of the attenuated influence of the atmospheric and oceanic circulations and the large areas of the Arctic Ocean and adjacent seas not covered by sea ice, the climatic spatiotemporal differences are lesser in summer than in winter.

Snow Distribution and Melt Modeling for Mittivakkat Glacier, Ammassalik Island, Southeast Greenland

Abstract A physically based snow-evolution modeling system (SnowModel) that includes four submodels—the Micrometeorological Model (MicroMet), EnBal, SnowPack, and SnowTran-3D—was used to simulate five full-year evolutions of snow accumulation, distribution, sublimation, and surface melt on the Mittivakkat Glacier, in southeast Greenland. Model modifications were implemented and used 1) to adjust underestimated observed meteorological station solid precipitation until the model matched the observed Mittivakkat Glacier winter mass balance, and 2) to simulate glacier-ice melt after the winter snow accumulation had ablated. Meteorological observations from two meteorological stations were used as model inputs, and glaciological mass balance observations were used for model calibration and testing of solid precipitation observations. The modeled end-of-winter snow-water equivalent (w.eq.) accumulation increased with elevation from 200 to 700 m above sea level (ASL) in response to both elevation and topographic...

Observed runoff, jökulhlaups and suspended sediment load from the Greenland ice sheet at Kangerlussuaq, West Greenland, 2007 and 2008

This study fills the gap in hydrologic measurements of runoff exiting a part of the Greenland Ice Sheet (GrIS), the Kangerlussuaq drainage area, West Greenland. The observations are of value for obtaining knowledge about the terrestrial freshwater and sediment output from part of the GrIS and the strip of land between the GrIS and the ocean, in the context of varying ice sheet surface melt and influx entering the ocean. High-resolution stage, discharge and suspended sediment load show a decrease in runoff of {approx} 25% and in sediment load of {approx} 40% from 2007 to 2008 in response to a decrease in the summer accumulated number of positive degree days. During the 2007 and 2008 runoff season, joekulhlaups are observed at Kangerlussuaq, drained from an ice-dammed lake at the margin of the GrIS.

Influence of wind speed on rainsplash erosion

Abstract Measurement of soil splash erosion on an event-based scale under natural rainfall was carried out on a field plot. Kinetic energy of precipitation was calculated according to a model that incorporates horizontal terminal velocities of raindrops induced by wind speed. A digital raingauge with a high output resolution was used to measure precipitation. Erosivity indexes were worked out based on the assumption that those minutes with the highest energy input in an event are decisive for soil detachment.

HYDROLOGY AND TRANSPORT OF MATERIAL IN THE SERMILIK AREA 1972

Hasholt, B., 1976; Hydrology and transport of material in the Sermilik area 1972. Geografisk Tidsskrift 75: 30–39 Kobenhavn june 1976. Investigations of water discharge and transport of material have been carried out in the area around the Mitdluagkat glacier in East Greenland. Precipitation and snow-melt were measured and compared with the discharge. The relationship between stage, discharge and concentration of suspended sediments were found, and the results were used to calculate hourly values of suspended sediment transport. In a few cases bed-load and dissolved load were measured at the same time as suspended load. The ratio between the transport components has been used to estimate the total load into the sea.

Climatic conditions at the Mittivakkat Glacier catchment (1994–2006), Ammassalik Island, SE Greenland, and in a 109-year perspective (1898–2006)

Abstract Geografisk Tidsskrift, Danish Journal of Geography 108(1):51–72, 2008 The present-day climate in the Mittivakkat Glacier catchment (65°N), Southeast Greenland, is investigated spatiotemporally based on time series (13 years, 1994–2006) and standard synoptic climate data from the meteorological station in Tasiilaq (Ammasslik), covering 109 years (1898–2006). Within the catchment, meteorological conditions are monitored at the coast (Station Coast, 25 m a.s.l.) for the period 1998–2006 and in the glacier area (Station Nunatak 515 m a.s.l.)for 1994–2006. During this 13-year period, solar radiation shows increasing values, averaging 0.5 W m−2 y−1, at the nunatak and decreasing values, averaging 1.4 Wm−2 y−1, at the coast. The mean annual solar radiation at Station Coast is 102 Wm−2y−1, which is about 10% lower than at Station Nunatak, and is probably caused by increasing and higher percentages of dense clouds and sea fog in the coastal area. The mean annual air temperature is increasing by 0.10.°C y−1 at the nunatak and by 0.05°C y−1 at the coast, extending the thawing periods by about 50 days and 5 days, respectively. A snow-free period of 64 days is observed at the nunatak. The coastal area is highly dominated by air temperature inversion and sea breezes during spring and summer, strongly controlling the lapse rates within the catchments. The glacier area is highly dominated by katabatic fall winds, resulting in an almost total lack of calm periods. The wind speed is highest during winter, with mean average values around 6.0 m s−1, and gusts up to 35.0 m s−1. The total annual precipitation varies from 1,851 mm w.eq. y−1 at the nunatak (solid precipitation: 80%, mixed: 6%, and liquid: 14%) to 1,428 mm w.eq. y−1 at the coast (53%, 31%, and 16%), covering an average positive orographic effect for solid precipitation during winter (113 mm w.eq. 100 m−1) and a negative effect for liquid precipitation during summer (-52 mm w.eq. 100 m−1). Over the last 109 years (1898–2006) precipitation in the catchment has increased about 85 mm w.eq., covering two significant precipitation-rich periods: 1901–1914 (1,560 mm w.eq. y−1) and 1963–1978 (1,563 mm w.eq. y−1). Mean annual air temperature in the catchment has generally increased 0.2°C through the 109-year period, most significantly ∼2.7°C within the last 25 years. The warmest 10-year period since 1898 was 1938–1947, showing an annual average of -1.83°C, while 1997–2006 was the warmest 10- year period within the last 60 years, with an annual average of—2.10°C.

ET FORSØG PÅ EN KLIMATISK- HYDROLOGISK REGIONSINDDELING AF HOLSTEINSBORG KOMMUNE (SISIMIUT)

Hasholt, B. & H. Sogaard 1978: Et forsog pa en klimatisk-hydrologisk regionsinddeling af Holsteinsborg kommune (Sisimut). Geografisk Tidsskrift 77: 72–92. Kobenhavn juni 1,1978. The Holsteinsborg municipality (Sisimut) has been divided into climatic and hydrological regions. The investigation is of a preliminary character due to the limited possibilities for field work. The regionalization is based upon selected climatological and hydrological parameters; these were primarily snow cover (precipitation), potential evapotranspiration, run-off, and temperature. Measurements of water quality have been used as indicator of the aridity in the area.

Sedimentation in arctic proglacial lakes: Mittivakkat Glacier, south‐east Greenland

Several sediment cores were collected from two proglacial lakes in the vicinity of Mittivakkat Glacier, southeast Greenland, in order to determine sedimentation rates, estimate sediment yields and identify the dominant sources of the lacustrine sediment. The presence of varves in the ice-dammed Icefall Lake enabled sedimentation rates to be estimated using a combination of X-ray photography and down-core variations in 137 Cs activity. Sedimentation rates for individual cores ranged between 0.52 and 1.06 g cm ˇ2 year ˇ1 , and the average sedimentation rate was estimated to be 0.79 g cm ˇ2 year ˇ1 . Despite considerable down-core variability in annual sedimentation rates, there is no significant trend over the period 1970 to 1994. After correcting for autochthonous organic matter content and trap eAciency, the mean fine-grained minerogenic sediment yield from the 3. 8k m 2 basin contributing to the lake was estimated to be 327 t km ˇ2 year ˇ1 . Cores were also collected from the topset beds of two small deltas in Icefall Lake. The deposition of coarse-grained sediment on the delta surface was estimated to total in excess of 15 cm over the last c. 40 years. In the larger Lake Kuutuaq, which is located about 5 km from the glacier front and for which the glacier represents a smaller proportion of the contributing catchment, sedimentation rates determined for six cores collected from the centre of the lake, based on their 137 Cs depth profiles, were estimated to range between 0.05 and 0.11 g cm ˇ2 year ˇ1 , and the average was 0.08 g cm ˇ2 year ˇ1 . The longer-term (c. 100‐150 years) average sedimentation rate for one of the cores, estimated from its unsupported 210 Pb profile, was 0.10‐0.13 g cm ˇ2 year ˇ1 , suggesting that sedimentation rates in this lake have been essentially constant over the last c. 100‐150 years. The average fine-grained sediment yield from the 32. 4k m 2 catchment contributing to the lake was estimated to be 13 t km ˇ2 year ˇ1 . The 137 Cs depth profiles for cores collected from the topset beds of the delta of Lake Kuutuaq indicate that in excess of 27 cm of coarse-grained sediment had accumulated on the delta surface over the last approximately 40 years. Caesium-137 concentrations associated with the most recently deposited (uppermost) fine-grained sediment in both Icefall Lake and Lake Kuutuaq were similar to those measured in fine-grained sediment collected from steep slopes in the immediate proglacial zone, suggesting that this material, rather than contemporary glacial debris, is the most likely source of the sediment deposited in the lakes. This finding is confirmed by the 137 Cs concentrations associated with suspended sediment collected from the Mittivakkat stream, which are very similar to those for proglacial material. Copyright # 2000 John Wiley & Sons, Ltd.

Sediment plumes as a proxy for local ice-sheet runoff in Kangerlussuaq Fjord, West Greenland

Meltwater runoff is an important component of the mass balance of the Greenland ice sheet (GrIS) and contributes to eustatic sea-level rise. In situ measurements of river runoff at the ! 325 outlets are nonexistent due to logistical difficulties. We develop a novel methodology using satellite observations of sediment plumes as a proxy for the onset, duration and volume of meltwater runoff from a basin of the GrIS. Sediment plumes integrate numerous poorly constrained processes, including meltwater refreezing and supra- and englacial water storage, and are formed by meltwater that exits the GrIS and enters the ocean. Plume characteristics are measured in Moderate Resolution Imaging Spectroradiometer (MODIS, band 1, 250m) satellite imagery during the 2001-08 melt seasons. Plume formation and cessation in Kangerlussuaq Fjord, West Greenland, are positively correlated (r 2 =0.88, n=5, p<0.05; r 2 =0.93, n=5, p<0.05) with ablation onset and cessation at the Kangerlussuaq Transect automatic weather station S5 (490ma.s.l., 6km from the ice margin). Plume length is positively correlated (r 2 =0.52, n=35, p<0.05) with observed 4day mean Watson River discharge throughout the 2007 and 2008 melt seasons. Plume length is used to infer instantaneous and annual cumulative Watson River discharge between 2001 and 2008. Reconstructed cumulative discharge values overestimate observed cumulative discharge values for 2007 and 2008 by 15% and 29%, respectively.

Surface Mass Balance and Runoff Modeling Using HIRHAM4 RCM at Kangerlussuaq (Søndre Strømfjord), West Greenland, 1950-2080

A regional atmospheric model, the HIRHAM4 regional climate model (RCM) using boundary conditions from the ECHAM5 atmosphere‐ocean general circulation model (AOGCM), was downscaled to a 500-m gridcell increment using SnowModel to simulate 131 yr (1950‐2080) of hydrologic cycle evolution in west Greenland’s Kangerlussuaq drainage. Projected changes in the Greenland Ice Sheet (GrIS) surface mass balance (SMB) and runoff are relevant for potential hydropower production and prediction of ecosystem changes in sensitive Kangerlussuaq Fjord systems. Mean annual surface air temperatures and precipitation in the Kangerlussuaq area were simulated to increase by 3.48C and 95 mm water equivalent (w.eq.), respectively, between 1950 and 2080. The local Kangerlussuaq warming was less than the average warming of 4.88C simulated for the entire GrIS. The Kangerlussuaq SMB loss increased by an average of 0.3 km 3 because of a 0.4 km 3 rise in precipitation, 0.1 km 3 rise in evaporation and sublimation, and 0.6 km 3 gain in runoff (1950‐2080). By 2080, the spring runoff season begins approximately three weeks earlier. The average modeled SMB and runoff is approximately 20.1 and 1.2 km 3 yr 21 , respectively, indicating that ;10% of the Kangerlussuaq runoff is explained by the GrIS SMB net loss. The cumulative net volume loss (1950‐2080) from SMB was 15.9 km 3 , and runoff was 151.2 km 3 w.eq. This runoff volume is expected to have important hydrodynamic and ecological impacts on the stratified salinity in the Kangerlussuaq Fjord and on the transport of freshwater to the ocean.